"Steven Sinofsky has decided to leave the company. Steven joined Microsoft in 1989 as a software development engineer and has contributed to the company in many ways from his work as a technical adviser to Bill Gates, to leading the evolution of the Microsoft Office business, to his direction and successful leadership of Windows and Windows Live as well as Surface [Microsoft's tablet, which has received mostly poor reviews]. I am grateful for the work that Steven has delivered in his time at our company."

Julie Larson-Green, who was instrumental in the development of the Metro UI in Windows Phone and now Windows 8, as well as the ribbon-oriented overhaul of Office, will take over Sinofsky's role, managing the Windows, Windows Live, and Surface product teams.

Some commentators have complained that Sinofsky has bungled the Windows transition by not dropping the legacy Windows 7 environment, which coexists awkwardly with Metro in Windows 8, while others have complained he has pushed Windows too far into alien territory, making it too unfamiliar to users. However, Larson-Green's appointment as his successor suggests Ballmer is committed to the radical rethinking of Windows that Sinofsky championed.

Ballmer has seen several high-profile technology executives depart in recent years -- many also tipped to be his successor -- including Bob Muglia and Ray Ozzie.

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